1. Technical Field
The present invention relates to an apparatus for biologic fluid analyses in general, and to cartridges for acquiring, processing, and containing biologic fluid samples for analysis in particular.
2. Background Information
Historically, biologic fluid samples such as whole blood, urine, cerebrospinal fluid, body cavity fluids, etc., have had their particulate or cellular contents evaluated by smearing a small undiluted amount of the fluid on a slide and evaluating that smear under a microscope. Reasonable results can be gained from such a smear, but the cell integrity, accuracy and reliability of the data depends largely on the technician's experience and technique.
In some instances, constituents within a biological fluid sample can be analyzed using impedance or optical flow cytometry. These techniques evaluate a flow of diluted fluid sample by passing the diluted flow through one or more orifices located relative to an impedance measuring device or an optical imaging device. A disadvantage of these techniques is that they require dilution of the sample, and fluid flow handling apparatus.
It is known that biological fluid samples such as whole blood that are quiescently held for more than a given period of time will begin “settling out”, during which time constituents within the sample will stray from their normal distribution. If the sample is quiescently held long enough, constituents within the sample can settle out completely and stratify (e.g., in a sample of whole blood, layers of white blood cells, red blood cells, and platelets can form within a quiescent sample). As a result, analyses on the sample may be negatively affected because the constituent distribution within the sample is not a naturally occurring distribution.
What is needed is an apparatus for evaluating a sample of substantially undiluted biologic fluid, one capable of providing accurate results, one that does not require sample fluid flow during evaluation, one that can perform particulate component analyses, and one that is cost-effective.